Notes Payable (Credit Facility Table) (Details)	12 Months Ended
	Dec. 31, 2012
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.50%
Leverage ratio, upper limit (percent)	60.00%
Less than or equal to 40%
Line of Credit Facility [Line Items]
Annual Facility Fee (percent)	0.20%
Leverage ratio, upper limit (percent)	40.00%
Greater than 40% but less than or equal to 50%
Line of Credit Facility [Line Items]
Annual Facility Fee (percent)	0.25%
Leverage ratio, upper limit (percent)	50.00%
Leverage ratio, lower limit (percent)	40.00%
Greater than 50% but less than or equal to 55%
Line of Credit Facility [Line Items]
Annual Facility Fee (percent)	0.35%
Leverage ratio, upper limit (percent)	55.00%
Leverage ratio, lower limit (percent)	50.00%
Greater than 55% but less than or equal to 60%
Line of Credit Facility [Line Items]
Annual Facility Fee (percent)	0.40%
Leverage ratio, upper limit (percent)	60.00%
Leverage ratio, lower limit (percent)	55.00%
Base rate [Member] | Less than or equal to 40%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.50%
Base rate [Member] | Greater than 40% but less than or equal to 50%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.60%
Base rate [Member] | Greater than 50% but less than or equal to 55%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.90%
Base rate [Member] | Greater than 55% but less than or equal to 60%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.10%
LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.00%
LIBOR [Member] | Less than or equal to 40%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.50%
LIBOR [Member] | Greater than 40% but less than or equal to 50%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.60%
LIBOR [Member] | Greater than 50% but less than or equal to 55%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.90%
LIBOR [Member] | Greater than 55% but less than or equal to 60%
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	2.10%